Recently, with increasing development of information industries, portable information devices such as notebook computers, mobile phones or personal digital assistants are widely used in many instances. In a case that a portable information device is used in a dim environment, the numbers and characters marked on the keys of the keyboard of the portable information device are not clearly visible. In other words, the dim environment becomes hindrance from operating the keyboard. In addition, if the keyboard is used in the dim environment, the user is readily suffered from vision impairment. For solving these drawbacks, a luminous keyboard has been disclosed. The luminous keyboard could be used in the dim environment in order to enhance the applications thereof. Moreover, by changing the arrangement of luminous regions, the information device having the luminous keyboard is more aesthetically-pleasing and thus the competiveness thereof is enhanced.
FIG. 1 is a schematic cross-sectional view illustrating a conventional luminous keyboard. As shown in FIG. 1, the luminous keyboard 1 comprises a reflector 11, a light guide plate 12, a base pate 13, a membrane circuit member 14, plural keys 15, and light-emitting elements 16. The membrane circuit member 14 comprises a lower wiring board 141, an upper wiring board 142, and an intermediate board 143. The intermediate board 143 is arranged between the lower wiring board 141 and the upper wiring board 142. The lower wiring board 141, the intermediate board 143 and the upper wiring board 142 are made of a transparent light-guiding material. The transparent light-guiding material includes for example polycarbonate (PC) or polyethylene terephthalate (PET).
Please refer to FIG. 2, which is a schematic exploded view illustrating a membrane circuit board of the luminous keyboard of FIG. 1. The lower wiring board 141 has a first circuit pattern 1411. The first circuit pattern 1411 comprises plural silver paste conductor lines 14111 and plural lower contacts 14112. The upper wiring board 142 has a second circuit pattern 1421. The second circuit pattern 1421 comprises plural silver paste conductor lines 14211 and plural upper contacts 14212. The intermediate board 143 has plural perforations 1431 corresponding to the plural lower contacts 14112 and the plural upper contacts 14212. Each of the upper contacts 14212 and the corresponding lower contact 14112 are collectively defined as a membrane switch 144.
The key base plate 13 is disposed under the membrane circuit member 14. In addition, the key base plate 13 comprises plural openings 131, a first fixing structure 132, and a second fixing structure 133. Each key 15 comprises a keycap 151, an elastic element 152, and a scissors-type connecting element 153. The keycap 151 comprises a first keycap fixing structure 1511 and a second keycap fixing structure 1512. The scissors-type connecting element 153 comprises a first frame 1531 and a second frame 1532. In addition, the elastic element 152 is arranged between the keycap 151 and the membrane circuit member 14.
The membrane circuit member 14 further comprises apertures 145 and 146 (see FIG. 1). The first fixing structure 132 and the second fixing structure 133 are penetrated through the apertures 145 and 146, respectively. A first end 1531A of the first frame 1531 is connected to the second fixing structure 133, and a second end 1531B of the first frame 1531 is connected to the first keycap fixing structure 1511. In addition, a second end 1532A of the second frame 1532 is connected to the first fixing structure 132, and a second end 1532B of the second frame 1532 is connected to the second keycap fixing structure 1512.
When any key 15 is depressed and moved downwardly relative to the key base plate 13, the first frame 1531 and the second frame 1532 of the scissors-type connecting element 153 are switched from an open-scissors state to a folded state. Moreover, as the keycap 151 is moved downwardly to compress the elastic element 152, the elastic element 152 is sustained against a corresponding upper contact 14212. Consequently, the upper contact 14212 is inserted into a corresponding perforation 1431 to touch the corresponding lower contact 14122. In such way, the corresponding membrane switch 144 is electrically conducted, and the luminous keyboard 1 generates a corresponding key signal. Whereas, when the depressing force exerted on the key 15 is eliminated, an elastic force provided by the elastic element 152 is acted on the keycap 151. Due to the elastic force, the keycap 151 is moved upwardly relative to the key base plate 13. Meanwhile, the first frame 1531 and the second frame 1532 of the scissors-type connecting element 153 are switched from the folded state to the open-scissors state, and the keycap 151 is returned to its original position.
The light-emitting elements 16 are located at bilateral sides of the light guide plate 12 for emitting light beams. The light beams are incident into the light guide plate 12. The light guide plate 12 is disposed on the reflector 11. Plural light-guiding dots 121 are formed on a bottom surface of the light guide plate 12 for collecting and scattering the light beams. The light-guiding dots 121 are aligned with corresponding keys 15. After the light beams are incident into the light guide plate 12, the light beams are diffused into the whole light guide plate 12. Due to the ink property of the light-guiding dots 121, the light beams will be scattered upwardly or downwardly. The portions of the light beams that are scattered upwardly will be sequentially transmitted through the openings 131 of the key base plate 13 and the membrane circuit member 14 and directed to the plural keys 15. The portions of the light beams that are scattered downwardly will be reflected by the reflector 11, and the reflected light beams are also directed upwardly. In such way, the light beams provided by the light-emitting elements 16 can be well utilized to illuminate the plural keys 15. However, the conventional luminous keyboard 1 still has the following drawbacks.
Firstly, although the reflector 11 can facilitate the light beams which are scattered downwardly from the light-guiding dots 121 to be reflected upwardly, since the material of the reflector 11 of the conventional luminous keyboard 1 is light-transmissible, some of the light beams which are scattered downwardly from the light-guiding dots 121 may be transmitted through the reflector 11. Under this circumstance, a portion of the light amount is lost.
Secondly, please also refer to FIG. 3. FIG. 3 schematically illustrates a light path in the lower wiring board of the membrane circuit member of FIG. 2. As shown in FIG. 3, the first circuit pattern 1411 is formed on a top surface of the lower wiring board 141, and comprises plural silver paste conductor lines 14111. Since these silver paste conductor lines 14111 have functions of collecting and scattering the light beams, after the light beams L1 provided by the light-emitting elements 16 are introduced into the lower wiring board 141 through the openings 131 of the key base plate 13, the light beams L2 passing through the silver paste conductor lines 14111 of the first circuit pattern 1411 seem very bright. Since most of the silver paste conductor lines 14111 are not aligned with the keys, the amount of the light beams to be directed to the keys 15 to illuminate the keys 15 are consumed by the silver paste conductor lines 14111. That is, although the light beams L1 should be mostly directed to the keys 15 according to the original design, the silver paste conductor lines 14111 may consume the amount of the light beams L2 because of the characteristics of the silver paste conductor lines 14111. Consequently, only the light beams L3 are retained to be utilized by the luminous keyboard 1. Under this circumstance, the keys 15 of the luminous keyboard 1 fail to be effectively illuminated.
FIG. 4 is a schematic cross-sectional view illustrating another conventional luminous keyboard. Except for the following items, the configurations of the luminous keyboard of FIG. 4 are identical to those of FIG. 1, and are not redundantly described herein. For example, the light-emitting elements 96 are located at bilateral sides of the lower wiring board 941 of the membrane circuit member 94. In addition, the lower wiring board 941 is made of a light-guiding material. Plural light-guiding dots 921 are formed on the lower wiring board 941 for collecting and scattering the light beams. In other words, since the lower wiring board 941 of the membrane circuit member 94 has the light-guiding function, the reflector 11 and the light guide plate 12 used in the conventional luminous keyboard 1 may be omitted. Under this circumstance, the thickness of the luminous keyboard of FIG. 4 is reduced.
However, the conventional luminous keyboard of FIG. 4 still has the above two drawbacks of the conventional luminous keyboard of FIG. 1. In addition, the membrane circuit member 94 further comprises apertures 945 and 946. A first fixing structure 932 and a second fixing structure 933 of the key base plate 93 are penetrated through the apertures 945 and 946, respectively. Consequently, the light-guiding function of the lower wiring board 941 of the membrane circuit member 94 is discontinuous. That is, the light beams from the light-emitting elements 96 fail to be transmitted through the regions of the lower wiring board 941 corresponding to the apertures 945 or 946. Under this circumstance, the illuminating efficacy of the luminous keyboard 9 is impaired.
From the above discussions, the light utilization efficiency of the conventional luminous keyboard 1 or 9 is unsatisfied. Therefore, there is a need of providing a luminous keyboard with enhanced light utilization efficiency.